You know the end song, Diamond Meditation? Well, after listening to it like 500 times, I picked up some sounds from mario paint composer. At one point in the background, you can hear an acoustic guitar, and the twinkle in the beginning is similar to the star instrument. And you can hear the cat sound in the background.

That song was created by troupe in an one-hour music creation competition. In those, the contestants gets a pre-made sample pack when the competition begins and have to create a song with those sounds in one hour. Troupe did an amazing job on his and I asked if I could put it in the game.

The explanation must simply be that he got a mario paint sample pack to create the song with.